Bob Reed, head of Anglo-European school, said colleges like his are fighting an English indifference to other tongues.
All pupils at the specialist college in Ingatestone, Essex, must study a foreign language in the sixth form, although inspectors have said this can be "a barrier to some students achieving their goals".
Mr Reed said: "We need to make languages compulsory and show young people why they should learn a language.
"We are unlikely to survive economically at our current level (of foreign language competence). In ten years, English will be the second language in the United States, behind Spanish."